Polyolefin resins have advantages in their excellent moldability, heat resistance, mechanical properties and low specific gravities, and have been widely used for films, sheets and various molded articles (e.g., structural parts). However, transparencies of polyolefin resins have not been always good.
This drawback is due to crystallinity of polyolefin resins, so that various crystalline nucleating agents have been widely used to improve transparency of polyolefin resins and to add heat resistance and mechanical strength thereto. Examples of such crystalline nucleating agent include compounds such as metal salts of carboxylic acids such as sodium benzoate, aluminum 4-tert-butylbenzoate, sodium adipate and disodium bicyclo[2.2.1]heptane-2,3-dicarboxylate; metal salts of phosphates such as sodium bis(4-tert-butylphenyl)phosphate, sodium 2,2′-methylenebis(4,6-di-tert-butylphenyl)phosphate and lithium 2,2′-methylenebis(4,6-di-tert-butylphenyl)phosphate; and derivatives of polyols such as dibenzylidene sorbitol, bis(methylbenzylidene)sorbitol and bis(dimethylbenzylidene)sorbitol.
Addition of amide compounds to improve properties of polyolefin resins such as polyethylene, polypropylene, polybutene-1 and 1,2-polybutadiene is widely known, for example as described in Patent Documents 1 to 9 described below.
In Patent Document 1, blending of a fatty acid diamide compound of phenylenediamine to inhibit degradation of polypropylene contacting with heavy metals such as copper is proposed, and an inhibitory effect on degradation due to a heavy metal is shown. In Patent Document 2, improvement of heat-sealing properties and transparency by blending of a bisamide compound to a polyolefin polymer containing not less than 5% by weight of polybutene-1 is disclosed. In Patent Document 3, addition of an amide compound obtained from a diamine and a monocarboxylic acid to polypropylene to obtain a crystalline polypropylene resin composition containing β crystals in a large amount is disclosed. In Patent Document 4, a compound obtained by reacting naphthalenedicarboxylic acid or biphenyldicarboxylic acid with a monoamine is proposed.
In Patent Documents 5 to 9, methods wherein a polyamine amide compound is included in polypropylene resins, polyethylene resins, polyester resins, polyamide resin, and crystalline synthetic resins called generically engineering plastics, respectively, are proposed.
Patent Document 1: Japanese Unexamined Patent Application Publication No. 50-105558
Patent Document 2: Japanese Unexamined Patent Application Publication No. 51-114482
Patent Document 3: Japanese Unexamined Patent Application Publication No. 6-107875
Patent Document 4: Japanese Unexamined Patent Application Publication No. 5-310665
Patent Document 5: Japanese Unexamined Patent Application Publication No. 6-220269
Patent Document 6: Japanese Unexamined Patent Application Publication No. 6-234890
Patent Document 7: Japanese Unexamined Patent Application Publication No. 6-263969
Patent Document 8: Japanese Unexamined Patent Application Publication No. 6-271762
Patent Document 9: Japanese Unexamined Patent Application Publication No. 8-157640